Method for ultrasonic inspection of irregular and variable shapes

Abstract

System and method for enabling ultrasonic inspection of a variable and irregular shape. The system comprises one or more ultrasonic pulser/receivers, one or more ultrasonic transducer arrays, a shoe or jig to hold and position the array(s), data acquisition software to drive the array(s), and data analysis software to select a respective best return signal for each pixel to be displayed. This system starts with information about the general orientation of the array relative to the part and a general predicted part shape. More specific orientation of the transmitted ultrasound beams relative to the part surface is done electronically by phasing the elements in the array(s) to cover the expected (i.e., predicted) surface as well as the full range of part surface variability.

The invention claimed is: 
     
       1. A method for inspecting a portion of a part having a surface of unknown radiused shape, the method comprising:
 (a) positioning and orienting a linear array of ultrasonic transducer elements at a location whereat the linear array can be operated to transmit focused and steered ultrasonic beams in a scan plane that will impinge on a radiused surface of the part having a curved concave profile in the scan plane; 
 (b) while the linear array is stationary at said location, electrically pulsing the ultrasonic transducer elements of different apertures of the linear array using phasing to transmit a sequence of successive focused and steered ultrasonic beams directed toward one and the same target location on the radiused surface, each focused and steered ultrasonic beam being formed by pulsing the ultrasonic transducer elements of a respective one of the different apertures to produce a respective focused ultrasonic beam having a respective different steering angle; 
 (c) while the linear array is stationary at said location and after the ultrasonic transducer elements making up each aperture have been pulsed, forming electrical signals from the ultrasonic transducer elements of the respective aperture into a respective return signal representing a respective echo returned to the respective aperture from the target location on the radiused surface following electrical pulsing of the ultrasonic transducer elements of the respective aperture; 
 (d) processing said return signals to derive respective values of a parameter characterizing said return signals from the target location; and 
 (e) selecting one of said respective parameter values that satisfies a first condition, 
 wherein steps (b) through (e) are repeated for each of a multiplicity of target locations disposed on the radiused surface at spaced intervals along a scan line in the scan plane. 
 
     
     
       2. The method as recited in  claim 1 , wherein said parameter is amplitude and said first condition is having the greatest amplitude. 
     
     
       3. The method as recited in  claim 1 , further comprising displaying a pixel having a value which is a function of at least said selected parameter value. 
     
     
       4. The method as recited in  claim 1 , further comprising:
 selecting another of said respective parameter values that satisfies said first condition or a second condition; and 
 displaying a pixel having a value which is a function of at least said one and said another selected parameter values. 
 
     
     
       5. The method as recited in  claim 1 , further comprising supplying fluid acoustic couplant into a space between the linear array and the part, wherein step (d) comprises applying respective gains to said respective return signals, said gains being selected to compensate for different amounts of energy loss caused by transmission inefficiency at higher angles, said respective gains being a function of distance of travel of each echo through said fluid acoustic couplant.